Tough epoxy resin systems for cryogenic applications

This work presents the development of new epoxy systems that combine high fracture toughness at cryogenic temperatures ( ) with a slow curing reaction (long pot life) and a glass transition temperature between and , ensuring good mechanical performance at room temperature. This was achieved by incorporating varying amounts and types of short-chain alkylamines into epoxy networks based on bisphenol A diglycidyl ether (DGEBA) crosslinked with metaphenylene diamine (MPD). This modification enhanced the cryogenic fracture toughness of the base system, DGEBA crosslinked with MPD, from 2 to . It has been suggested that the significantly improved cryogenic fracture toughness in systems with flexible aliphatic chain extenders might result from nano- or micro-phase separation, but X-ray scattering and dynamic mechanical spectroscopy did not provide conclusive evidence for this hypothesis. The required slow curing reaction was achieved by using a sterically hindered alkylamine (2-heptylamine) as chain extender, which increased the pot life more than twofold, resulting in resin formulations that combine a high cryogenic fracture toughness, a low viscosity and a long processing window at room temperature. • Design of epoxy resins with high cryogenic fracture toughness, long pot life and mechanical rigidity at room temperature. • High cryogenic fracture toughness due to incorporation of epoxide chain extenders consisting of flexible alkylamines. • Long processing lifetimes achieved by using sterically hindered alkylamines.